---
name: cometchat-android-v5-extensions
description: "Extension architecture for CometChat Android — ExtensionsDataSource, decorators, built-in extensions, and how to create custom extensions."
license: "MIT"
compatibility: "Android 7.0+; Java 8+; Kotlin 1.8+; com.cometchat:chat-uikit-android:5.x"
metadata:
author: "CometChat"
version: "3.0.0"
tags: "cometchat android extensions datasource decorator polls stickers collaborative"
---
> **Ground truth:** `com.cometchat:chat-uikit-android:5.x` (legacy/maintenance-only; +`calls-sdk-android:5.x`) — resolved AAR (javap) + `ui-kit/android`. **Official docs:** https://www.cometchat.com/docs/fundamentals/extensions-overview · **Docs MCP:** `claude mcp add --transport http cometchat-docs https://www.cometchat.com/docs/mcp` (or fetch the URL directly without MCP). Verify symbols against the installed package/source before relying on them.
> **Companion skills:** `cometchat-android-v5-customization` covers DataSource decorators;
> `cometchat-android-v5-features` covers the feature catalog.
## Purpose
This skill covers the CometChat extension architecture — how extensions plug into the UI Kit, the built-in extensions, and how to create custom ones.
---
## Use this skill when
- "How do extensions work?"
- "How do I add a custom extension?"
- "How do I disable an extension?"
- Working with `ExtensionsDataSource` or `ExtensionDecorator`
## Do not use this skill when
- Enabling a backend extension or AI feature → use `cometchat-android-v5-features` (which routes to `cometchat apply-feature <id> --app-id <X>`)
- Writing custom message templates → use `cometchat-android-v5-customization`
---
## 1. Extension architecture
Extensions are split into two class types:
- **Registrar** classes (e.g. `PollsExtension`, `StickerExtension`) — extend `ExtensionsDataSource`. These are what you pass to `setExtensions(...)` to enable a built-in extension.
- **Decorator** classes (e.g. `PollsExtensionDecorator`, `StickerExtensionDecorator`) — extend `DataSourceDecorator`. These are the runtime decorators that wrap the active `DataSource` chain. The kit creates them internally; you don't construct them directly.
```
ChatConfigurator.getDataSource()
└── SmartRepliesExtensionDecorator (created by SmartRepliesExtension)
└── PollsExtensionDecorator (created by PollsExtension)
└── StickerExtensionDecorator (created by StickerExtension)
└── MessagesDataSource (base)
```
## 2. Built-in extensions
| Extension | Package | What it adds |
|---|---|---|
| Polls | `com.cometchat.chatuikit.extensions.polls` | Poll creation and voting in messages |
| Stickers | `com.cometchat.chatuikit.extensions.sticker` | Sticker keyboard and sticker bubbles |
| Collaborative Document | `com.cometchat.chatuikit.extensions.collaborative` | Shared document editing |
| Collaborative Whiteboard | `com.cometchat.chatuikit.extensions.collaborative` | Shared whiteboard |
| Smart Replies | `com.cometchat.chatuikit.extensions.smartreplies` | AI-powered reply suggestions |
| Message Translation | `com.cometchat.chatuikit.extensions.messagetranslation` | Translate messages |
| Text Moderation | `com.cometchat.chatuikit.extensions.textmoderation` | Profanity filtering |
| Thumbnail Generation | `com.cometchat.chatuikit.extensions.thumbnailgeneration` | Image thumbnails |
## 3. Enabling/disabling extensions
Extensions are enabled by default. To customize which extensions are active, pass a custom list to `UIKitSettingsBuilder`:
```java
List<ExtensionsDataSource> extensions = new ArrayList<>();
extensions.add(new PollsExtension()); // registrar, NOT PollsExtensionDecorator
extensions.add(new StickerExtension()); // registrar, NOT StickerExtensionDecorator
extensions.add(new SmartRepliesExtension());
// Omit extensions you don't want
UIKitSettings settings = new UIKitSettings.UIKitSettingsBuilder()
.setAppId(APP_ID)
.setRegion(REGION)
.setAuthKey(AUTH_KEY)
.setExtensions(extensions)
.build();
```
> **Why not `PollsExtensionDecorator`?** `*ExtensionDecorator` extends `DataSourceDecorator`, not `ExtensionsDataSource` — so it won't compile when added to a `List<ExtensionsDataSource>`. The kit's runtime decorator chain is built by the registrar's `enable()` method internally; you don't add decorators directly.
## 4. Creating a custom extension
A custom extension has TWO classes:
1. A **registrar** that extends `ExtensionsDataSource` (gets added to `setExtensions(...)`)
2. A **decorator** that extends `DataSourceDecorator` (created by the registrar via `ChatConfigurator.enable(...)`)
```java
// 1. Decorator — extends DataSourceDecorator, overrides per-message behavior
public class MyExtensionDecorator extends DataSourceDecorator {
public MyExtensionDecorator(DataSource dataSource) {
super(dataSource);
}
// Override methods to add custom behavior
}
// 2. Registrar — extends ExtensionsDataSource, implements getExtensionId() + addExtension()
public class MyExtension extends ExtensionsDataSource {
@Override
public String getExtensionId() {
return "my-custom-extension";
}
@Override
public void addExtension() {
// addExtension() is the ABSTRACT method you must implement. The inherited
// concrete enable() calls it after confirming the extension is on (dashboard).
ChatConfigurator.enable(dataSource -> new MyExtensionDecorator(dataSource));
}
}
// Then add the registrar to UIKitSettings:
extensions.add(new MyExtension());
```
---
## Hard rules
- **Two classes per extension.** A registrar (`ExtensionsDataSource`, implements abstract `getExtensionId()` + `addExtension()`; `enable()` is inherited) and a decorator (`DataSourceDecorator`, holds the per-message override). `setExtensions(...)` wants registrars; the chain builds decorators automatically.
- **Register after init.** `ChatConfigurator.enable()` must be called after `CometChatUIKit.init()` succeeds.
- **Backend extension toggle still applies.** Even if an extension is registered client-side, it needs to be enabled on the app's backend. Use `cometchat apply-feature <id> --app-id <X>` (the CLI hits the dashboard API). For dashboard-only extensions (Giphy / Stipop / Tenor / Chatwoot / Intercom — those needing third-party API keys), the user has to enter the third-party config in the dashboard manually.